The present invention relates to a diagnostic system for at least two control apparatus of a motor vehicle equipped with a defect or trouble memory and at least one self-diagnostic function, whereby the control apparatus are connected with each other by way of a defect or trouble lamp line connected to a defect or trouble lamp and of a diagnostic bus consisting of at least one initialization line, and whereby the diagnostic functions, respectively, a read-out of the defect memory by application of signal defined by their time duration (initialization time) on the initialization line are initiated at different switching conditions of an ignition switch and informations concerning the condition of the control apparatus and/or its peripherals can be indicated by way of the defect or trouble lamp in the form of a flashing code which can be detected and counted by the human eye.
By reason of the constantly increasing function volume and of the ever-increasing number of electronic control apparatus in motor vehicles, diagnostic systems equipped with defect or trouble memories and self-diagnostic functions are increasingly used for the same. The control apparatus are thereby generally connected with each other by way of a diagnostic bus with which an external test apparatus or a test apparatus of the vehicle itself is adapted to be connected.
In addition to large and expensive service shop-test apparatus by means of which a fully automatic diagnostic analysis with defect or trouble output in plain language alpha-numerical) is possible, also the very simple and cost-favorable diagnostic systems with flashing code output come into utilization with an ever-increasing extent; smaller service shops and repair shops can also afford to purchase these simple diagnostic systems.
For example, the fuel injection control apparatus LH-Jetronic LH 2.3, the ignition control apparatus EZ 121K and the engine control apparatus Motronic M 2.1 of the company Bosch (see, for example, SAE Paper 840 541) which are capable of self-diagnostic analysis, are equipped with such a diagnostic system. These control apparatus are connected with each other in the motor vehicles by way of an initialization line (test line) and a defect (trouble) lamp line. A key or momentary switch is connected with the test line by way of a plug-in connection, by means of which the test line can be momentarily connected to ground. A defect lamp (light diode) is either arranged in the instrument panel of the motor vehicle or is structurally combined with the momentary switch in a common housing.
A diagnostic analysis of the aforementioned control apparatus and also of further control apparatus capable of self-diagnostic analysis (insofar as they are equipped therefor), for example, of a charging pressure regulation, of an anti-lock system, of an air-conditioning system, etc., is now possible by means of such a simple control apparatus, i.e., the defect memories arranged in these control apparatus can be read out by the test apparatus; the defects which during the operation of the control apparatus have occurred in the control apparatus itself or at its peripheral, are stored in the defect memory. Similarly, for example, a diagnostic analysis of the adjusting members actuated by the control apparatus is possible, as well as a so-called "basic air-requirement adaptation" in the idling speed (adjustment of the idling desired rotational speed).
The diagnostic sequence will now be explained by reference to the example of the read-out of the defect memory and is realized as follows:
After plugging in the test apparatus in the initialization (test) line and the defect (trouble) lamp line, the ignition switch is displaced into its position "ignition on" and the initialization line is connected to ground by means of the momentary switch for 2.5 to 5 seconds initialization time). The control apparatus with highest priority then commences with the read-out of the first defect or trouble by way of the defect or trouble lamp line in the form of a flashing code detectable and readable by the human eye, whereby a serviceman counts the number of flashing pulses and has to coordinate the same to four different digits or places of a code word (with a maximum of 9 flashing pulses per digit or place). He then compares the thus-obtained code word with a table in which certain troubles or defects in certain control apparatus or the peripherals thereof are coordinated to the individual trouble code words.
After the serviceman has detected the trouble or defect code and has noted the same, he can read-out the next trouble or defect by a renewed initialization of the control apparatus initialization time 2.5 to 5 seconds by the momentary switch until at the end of a code appears, "no further defects present". He can then erase the defect memory of the control apparatus by application of a signal of an initialization period in excess of ten seconds and continue in the same manner with the read-out of the trouble or defect memory of the control apparatus with the next lower priority until he has read-out finally all trouble or defect memories of all control apparatus.
In a similar manner, also the adjusting member--and switching input-diagnostic analysis and the base air requirement adaptation are carried out, in which the flashing code represents, for example, an address of an activated adjusting member. The read-out of the trouble or defect takes place, however, strictly sequentially, control apparatus by control apparatus with decreasing priority and defect for defect so that, for example, a direct access to a certain control apparatus is not possible. If, for example, it is known that a trouble or defect has occurred in the air-conditioning system of the motor vehicle, then nonetheless at first all control apparatus with higher priority have to be diagnostically analyzed even though this in not necessary or not even interesting under certain circumstances.
Similarly, with this diagnostic system, a direct relation of the read-out trouble or defect to a certain control apparatus is only possible with great difficulty because the flashing code indicates only generally a trouble or defect. As a result thereof, the trouble or defect coordination and identification is rendered unnecessarily difficult, for example, when during the diagnostic sequence the serviceman has forgotten which control apparatus is being diagnostically analyzed by him at that time.
It is therefore the object of the present invention to improve the diagnostic system as regards the diagnostic sequence and the trouble or defect identification in that the diagnostic sequence is accelerated and rendered more comfortable and the error or trouble identification and coordination is facilitated.
The underlying problems are solved according to the present invention in that a diagnostic function of a control apparatus or device can be interrupted at any time and/or a next control apparatus with lower priority can be selected at any time by application of an additional signal on the initialization line by the momentary switch of defined duration and in that a predetermined information content is coordinated to the four flashing sequences or digits of the flashing code word in their timed sequence.
The advantages of the present invention reside above all in the accelerated and more comfortably constituted sequence of the diagnostic functions and of the improved trouble or defect identification as well as in the improved coordination of the code words to certain control apparatus. Further advantages are to be seen in the creation of a simple testing apparatus which counts flashing sequences of flashing codes, indicates the code in clear text or plain language and can apply on the initialization line signals of preselected defined duration on momentary switch depression.